This invention relates to a method and apparatus for singulating, debarking, scanning and automatically sawing and sorting logs into lengths. More particularly, this invention relates to a high product system and apparatus for processing raw logs into debarked optimum lengths for sawing into the maximum amount of lumber per log.
For raw logs to be cost effectively processed into random lengths without bark for use in a sawmill, it is important that this process is done with speed, accurate information obtained about the log, and accurate cutting into the maximum number of usable lumber per log. The speed requirement is determined in part by the efficient singulation of the logs from a log pile into the log processing system, in part by the rate at which bark can be removed optimally, with a minimum amount of white waste, in part by the rate at which the log can be quickly and accurately positioned and cut by the saws and in part by the rapid effective removal system of the random lengths. The accuracy of the information obtained about a log is determined by the type of conveying system, the type of scanner and whether the log is scanned with bark on or bark off. The accuracy of cutting the logs into lengths is determined in part by the required log process speed and in part by the system and equipment in which the log is positioned relative to the saw.
Considerable effort has been expended over the years to develop efficient and high speed log processing systems. The prior art that has been developed includes equipment and systems disclosed in the U.S. patents listed below.
U.S. Pat. No. 5,119,930, granted Jun. 9, 1992, Stelter, discloses and protects a single quadrant-type log sorter. Stelter, in FIGS. 1 and 2, illustrates in dotted lines, a counterweight 70 which reduces the force necessary to raise the quadrant 16. Stelter also discusses at column 4, lines 53-56, the use of a double-acting cylinder 56 so pressure may be provided on both sides of a piston to raise and lower the quadrant and rectify a portion of the live load. Stelter does not, however, disclose dual quadrants.
U.S. Pat. No. 5,722,475, granted Mar. 3, 1998, Lammi, discloses a design of ring type debarker using rotary cutting heads 23. The ring or rotor 4 can be varied in speed, as stated in the abstract, and in column 2, lines 60-63. The speed of the rotor disk 4 can be adjusted continuously due to variations in log diameter, surface finish, irregularities and the like. It is mentioned in column 2, lines 64-67, that the rotational speed of the cutting head should be kept nearly constant regardless of variations in the rotor speed. Lammi therefore does not disclose variable ring or rotor speed or variable force on the cutting blades.
U.S. Pat. No. 4,609,020, granted Sep. 2, 1986, Hutson, is one of several Hutson patents which disclose a log debarker system which has a rotor assembly 26 which uses a plurality of debarking tools 28 (knives), the combination rotating in a rotor housing assembly 24. There is no mention of varying the force on the debarking tools 28 or rotor or log feed speed as a function of diameter.
U.S. Pat. No. 5,117,881, granted Jun. 2, 1992, Simpson, assigned to Nicholson Manufacturing Company, discloses a ring type debarking apparatus which includes counterbalance weights 64 for rotary cutters 22. The counterbalance weights 64 offset centrifugal and gravitational forces. The debarker also includes rotary cutting units 18 on ends of swing arms 24. The debarker ring 22 rotates (see column 2, lines 8-9) but presumably at a constant speed. There is no mention of varying ring speed, tool tip force or log feed speed as a function of log diameter.
U.S. Pat. No. 4,330,019, granted May 18, 1982, Murphy et al., discloses a sawmill for cutting logs into lengths which allows for maximum use of the wood. An electronic scanner surveys the log as it is delivered to a support and obtains log profile data which is transmitted to a computer. Signals sent by the computer to each of the saws cause the saws to take up positions which ensure that the log is cut into optimum random lengths. The Murphy et al. system utilizes a reference datum line or cutting plane (see column 1, lines 55-56) for positioning the log. Murphy et al. disclose a xe2x80x9creach outxe2x80x9d cylinder 126 and an end plate, but these are used to assess the position of the butt end of the log and do not push the log into any particular position. The log therefore remains in its initial rest position. Murphy et al. also disclose a scanner 100 which may use conventional single or double axis techniques for scanning (see column 4, lines 28-29) as well as a master control unit 110.
U.S. Pat. No. 4,468,993, granted Sep. 4, 1984, McCown et al., discloses a log bucking station in which a log is scanned to determine its size and shape. The scan data is analyzed by a computer which determines the optimum locations for cuts on the log. The proposed cut locations are optically displayed on the log by a laser for inspection by the operator. The operator can overrule the computer. McCown et al. permit the distance between the pairs of saws to be varied because the saws run on tracks. By varying the distance between the two travelling saws 26 and 28, it is said that it is possible to optimize the saw cut locations.
The present invention overcomes or greatly reduces the disadvantages of known systems for processing raw logs into debarked random cut lengths prior to delivery of the logs to a chipping or log sawing apparatus.
The invention is directed to a log processing and cutting system comprising: (a) a log infeed deck; (b) a log feeder; (c) a dual quadrant singulator located downstream of the log feeder; (d) an infeed conveyor; (e) a log barker located downstream of the barker infeed conveyor; (f) a barker outfeed conveyor located downstream of the log debarker; (g) a bucking line scanner which scans the debarked log and by means of an associated computer, determines the log profile of the debarked log and determines optimum cutting locations on the log; (h) a conveyor located downstream of the bucking line scanner for conveying the scanned log to a bucking line; (i) a cradle in which the scanned log is held; (j) a bucking line positioner which contacts an end of the scanned log and moves it to an optimum position for cutting by a cut-off saw; (k) a bucking line cut-off saw which cuts the log at the optimum location determined by the computer from the log profile information ascertained by the scanner; (l) a bucking line outfeed conveyor located downstream of the cut-off saw for conveying away the cut log; and (m) a log sorter which directs the cut log to a log sorting station.
The dual quadrant singulator can comprise a lower quadrant singulator and an upper quadrant singulator, the pair of singulators operating in combination to single out and elevate individual logs.
The debarker can incorporate rotating rings, which can hold debarking knives and the force exerted on the cutting knives and the speed of rotation of the rings can be varied according to log profile characteristics of an individual log. The bucking line scanner can determine the log profile by three laser scans, to determine the volume and shape of the log being scanned at incremental log lengths.
The computer can instruct the cut-off saw to move in advance of the log reaching the cradle in order to minimize saw travel during the log cutting operation. The log positioner can comprise a hydraulic piston and cylinder, the piston extending a specified distance as determined by the computer, based on log profile and volume data as determined by the log scanner, and thereby positioning the log in optimum position.
The system can include a pair of spaced apart cut-off saws, the locations of the pair of cut-off saws being variable according to optimum saw location cut points on the log to be cut, as determined by the computer based on log scan data determined by the scanner.
The invention is also directed to a method of processing and cutting logs comprising: (a) singulating logs using a dual quadrant singulator; (b) debarking the logs using a variable speed ring and knife system; (c) scanning the debarked log by means of an associated computer, which determines the log profile of the debarked log and determines optimum cutting locations on the log; (d) conveying the scanned log to a bucking line cradle; (e) using a bucking line positioner which contacts an end of the scanned log and moves it to an optimum position for cutting; (f) cutting the log at the optimum locations as determined by the computer from the log profile information ascertained by the scanner and according to the positioner; (g) conveying the cut log away from the cutting area; and (h) sorting the cut log according to a command from the computer.
The dual quadrant singulator can comprise a lower quadrant singulator which can lift the log to a first elevation and an upper quadrant singulator, which can lift the log to a second elevation. The rotating rings of the debarker can hold cutting knives and the force exerted by the cutting knives on the log and the speed of rotation of the rings can be varied according to log profile characteristics of an individual log.
The scanning of the log can be done by three laser scans, which determine the volume and shape of the log being scanned at incremental log lengths. A computer can command a saw to move in advance of the log reaching the cradle to thereby minimize saw travel during the log cutting operation. The log can be positioned in the cradle by a piston which can extend a specified distance as determined by the computer, based on log profile and volume data as determined by the log scanner, and thereby positioning the log in optimum position. The log can be cut at two locations, the locations of the cuts being determined as optimum by the computer based on log scan data ascertained by the scanner.